Propeller blade



June 15, 1937. H, A, HALL 2,083,993

PROPELLER BLADE Original Filed June 19, 1936 j INVENTOR,

'1 i NW6; (0. Mae

20 I BY Bmfv 3$ A TTORNEYS.

Patented June 15, 1937 UNITED S'TTES PArENrorri 5 Claims. (01. -'159) This application is a division of applicants copending application Serial No. 86,091, filed June 19, 1936. The invention claimed herein relates to aircraft propellers, and has for its principal object the provision of blades of improved form whereby efiiciency is increased, and manufacturing and maintenance costs are reduced.

A second object is to provide improved shanks for the blades, whereby they may be securely held in suitable mountings, and which adapt them either for permanent positioning or for adjustability to vary their pitch angle. Still other objects and advantages of the invention will become apparent from the following specification, which should be read with the understanding that changes may be made, within the scope of the claims hereto appended, in. the form, construction and arrangement of the several parts herein described and illustrated, without departing from the spirit of the invention.

Reference will be made to the accompanying drawing, in which Fig. 1 is a side elevation of a propeller provided with my improved blades.

Fig. 2 is an end elevation. of one blade.

Fig. 3 is a rear elevation of one blade removed from the propeller hub, one of the shank filler members being removed.

Figs. 4 and 5 are transverse sections of the blade, taken on the respective lines 44 and 5-5 of Fig. 3.

Fig. 6 is a transverse section of a blade of slightly modified shape, taken approximately midway between the shank and the outer end or tip.

Fig. 7 is a transverse section through the shank of the blade, on the line 'l--l of Fig. 3, both shank filler members being shown in position.

In Figs. 2, 4;, 5 and 6 the vertical arrows 8 indicate the direction of flight, and the horizontal arrows 9 indicate the direction of rotation of the blade.

My improved blade may be mounted in any suitable propeller hub, such as that which forms the subject matter of my copending application referred to above. The construction of the hub and mounting form no part of the invention claimed herein, and therefore have been omitted from this specification. By way of illustration, there is shown in Fig. 1 a propeller having blades l0 projecting from a central hub H, the latter being mounted upon a shaft I2.

Each blade I0 is formed from a fiat piece, preferably of steel, beveled to a sharp leading edge I3, as shown in Figs. 2, 4, 5 and 6 in which the direction of flight is indicated by the arrow 8, and the. direction .of rotation of the blade by the arrow 9." The bevel M which produces the sharp leading edge does-not extend all the way to the base of the blade, leavinga shank portion l5 of reduced width and rectangular section, as shown in Figs. 3 and 7. This fiat, rectangular shank portion is interposed between, two semi-cylindrical hollowfiller members it, the edges of said membersbeing preferably welded to the blade, and forming with it a unitary cylindrical shank. The filler members I6 are provided with spaced annular flanges ii and I8, the latter being at their inner end, and the shank portion of the blade is provided with corresponding projections Ila and 18a whereby the flanges of the built-up cylindrical shank are made continuous. After being welded to the blade, the members It may be turned down in a lathe to make a cylindrical flanged shank adapted to fit accurately in whatever form of holding socket (not shown) may be provided in the hub l i. The flanges ll and [8 look the blade in said socket to prevent it from flying out endwise, and the cylindrical form of the shank enables it to be turned, if desired, to Vary its pitch angle.

The outer ends of the filler members iii are provided with enlarged semi-cylindrical flanges i9, Figs. 2, 3 and 7, which fit snugly against the flat faces of the blade throughout its entire width, as shown at 28, and are preferably welded thereto. These flanges i 9 provide a cylindrical shoulder (shown best in Fig. 2) at the base of the effective portion of the blade. The mounting of the blade is preferably such that said shoulder is flush with and forms a continuation of the outer surface of the hub H, as set forth more fully in my co-pending application referred to above.

The bevel l4, which produces the sharp leading edge of the blade, is formed upon its back, and increases in width from the outer end of the shank to the tip or outer end of the blade, where said blade is wedge shaped, as shown in Figs. 2, 3,

4 and 5. At the same time the blade is twisted slightly, as shown best in Fig. 2, to reduce the pitch angle of the pressure face 2! at said outer end. The plane of said bevel it therefore remains approximately perpendicular to the line of flight, which is its best position. The portion of the back of the blade near the trailing edge can also be beveled if desired, as shownat 22 in Fig. 6, to decrease weight, although I have found by actual experiment that efficiency is increased much more by beveling-the leading edge than the trailing edge.

It will be seen from the foregoing description that my construction provides a simple, efiicient, and inexpensive form of blade provided with a shank that can be securely held in the hub to prevent the blade fromrworking loose while permitting its pitch angle to be set at any desired value. 7

I claim:

1. In an air propeller, a blade formed from an.

initially flat strip of substantially rectangular cross section, the back of said blade being beveled to produce a sharp leading edge, said bevel increasing in width and the angle between it and the face of the blade decreasing from the inner end to the outer end, and said blade being twisted about its longitudinal axis to decrease the pitch angle of said face from said inner end to said outer end.

2. In an air propeller, a blade formed from an initially flat strip of rectangular cross section, one wider side of said strip having a bevel increasing in width from the inner to the outer end, said bevel reducing the thickness of the leading edge of the blade to a knife edge throughout its entire effective length.

3. In an air propeller, a blade formed from an initially flat strip of rectangular cross section, one wider side of said strip having a bevel increasing in width from the inner to the outer end to produce a sharp leading edge for the blade throughout its entire effective length, and said blade being twisted about its longitudinal axis to decrease its pitch angle from said inner end to said outer end.

4. In an air propeller, a blade formed from an initially fiat strip of substantially rectangular cross section, the back of said blade having a bevel increasing in width and decreasing in angularity with respect to the face of the blade from the inner end to the outer end, said blade being twisted about its longitudinal axis through approximately the same angular distance as the decrease in angularity of said bevel, and said blade being mounted with the plane of said bevel approximately perpendicular to the axis of the propeller. 

